The present invention relates to electrodes for electrochemical or related measurements, for example, HPLC-electrochemical, electrochemiluminescence, UV-electrochemistry, cyclic voltammetry measurements, and the like, and in particular to a solid-surface working electrode having replaceable tips.
The study of oxidation/reduction reactions in electrochemistry may use two or more solid surface electrodes in contact with an electrolyte. One electrode, termed a working electrode, may have a reactant applied to its surface whose interaction with the electrolyte is subject to the study. The reactant may be supported on a reactant substrate such as carbon nanotubes to enhance certain properties of the reactant materials by increasing the surface area, electrical conductivity, biocompatibility, reactant dispersion and the like.
The microstructure, cleanliness, and chemical composition of the working electrode surface greatly influence the measurement and use of the electrode. For frequently used glassy-carbon electrodes (GCE) or other kinds of metal electrodes, the surface to which the reactant or a reactant substrate is applied must be cleaned and may be pre-activated for use in a multi-step process. Such a process may include, for example, polishing the surface with a fine micro cloth and a successively finer 1.0, 0.3 and 0.05 μmα-alumina slurry until a mirror-like surface is obtained. A mirror-like surface is one that provides substantially specular reflection in visible light frequencies.
The electrode is rinsed with double distilled water (ddH2O) after each polishing. Sonication steps are performed consecutively in ethanol (or 1:1 HNO3/ethanol, 0.5 M H2SO4, cyclohexane etc.) and ddH2O, and the GCE is dried at room temperature (or by N2 flow). In this typical cleaning process, high-quality double-distilled ultra pure “type 1” water (e.g. Milli-Q water) with resistivity greater than 18.2 MΩ must be used throughout the process, including rinsing, sonication, and making solutions. After this clean-up, an electrochemical scan (typically cyclic voltammetry) should be performed to confirm that the scan conforms to the characteristics of a ‘fresh’ electrode of the same kind.
Such treatments (polishing and sonication) expose fresh new surfaces of the electrode and remove old carbon particles and the remains of polishing materials. However, the cleaning conditions, such as sonication time and polishing pressure and time, are critical and polishing on some types of abrasive containing pads can result in deactivating the surface. Repeated sonications may eventually destroy the electrode by compromising the seal between the carbon and the outer cladding material, (e.g. Teflon) while the use of large particles (e.g. large size of alumina powder) for polishing can create unrepairable surface defects, scratches and indentations, making the electrodes become abraded and suffer poor performance, resulting in inaccurate measurements and loss of use of electrodes. These cleaning and polishing steps are also very time-consuming and laborious. Similar problems affect working electrodes formed of other materials.